1. Field of the Invention
This application is related to ophthalmic devices. More particularly, this application is directed to ophthalmic devices that are configured not to degrade over the useful life of the ophthalmic device.
2. Description of the Related Art
A normally functioning human eye is capable of selectively focusing on either near or far objects through a process known as accommodation. Accommodation is achieved by inducing deformation in a lens located inside the eye, which is normally referred to as the “intraocular lens”. Such deformation is induced by muscles called ciliary muscles. As some individuals age, the ability to accommodate diminishes and these individuals cannot see up close without vision correction. If far vision also is deficient, such individuals are prescribed bifocal lenses.
While this approach is sometimes satisfactory, some have proposed implanting devices inside the eye to improve accommodation for older patients. One such implant is a pin-hole imaging device that can be implanted in the cornea of an eye. While this type of device has been discussed in various contexts, and a need for the device has been identified, no such device is currently on the market.
Several factors make a successful device of this type elusive. In particular, the device needs to improve the depth of field of a patient's vision and, because it is surgically implanted, the device has to have a very long life-span. No known device has been proposed that has an adequate life-span.
Because corneal implants are exposed to a great deal of sunlight during their lifetime, resistance to degradation of the polymer due to UV exposure is important. In the contact lens and IOL arts, commercially available stabilizers have been added to the lenses to prevent degradation of the lenses due to this exposure and also to exposure to UV light used as a means of sterilization. Stabilizers dissipate the energy of ultraviolet rays to prevent degradation of the lens material. The stabilizers may be physically combined with the polymer or they may be part of a monomer which is copolymerizable with the polymeric material which forms the lens. Copolymerization reduces extractability, a problem with many stabilizers that are merely physically combined with a polymer.